The present invention relates to novel polycarbonate and more particularly to polycarbonate which is excellent in transparency and also in flame retardance and impact resistance. 2. Description of Related Art
As polycarbonate having high flame retardance, for example, polycarbonate having a halogen-substituted phenoxy group (e.g., a pentabromophenoxy group, a tetrachlorophenoxy group,, a tribromophenoxy group and the like) at the terminal thereof (Japanese Patent Publication No. 40715/1971), a copolymer of tetrahalogenobisphenolsulfone and bisphenol A (BPA) (Japanese Patent Application Laid-Open No. 123204/1976), polycarbonate having an aromatic monosulfonyl group at the terminal thereof (Japanese Patent Application Laid-Open No. 21497/1979), a copolymer of tetrabromobisphenol A and BPA (Japanese Patent Application Laid-Open No. 155233/1982), and polycarbonate having a sulfonic acid salt group at the terminal thereof (PCT Japanese Patent Application Laid-Open No. 501212/1985) are known.
These conventional polycarbonates, however, are not sufficiently satisfactory in impact resistance or transparency although it is superior in flame retardance. That is, there has not been obtained polycarbonate which is superior in all of flame retardance, impact resistance, and transparency.
Even polycarbonate which has a small flow value and thus is suitable for extrusion molding, when an effective amount of tetrabromobisphenol A is added in order to impart flame retardance, suffers from a problem that it becomes difficult to pulverize the resulting polycarbonate in the course of production thereof.
In addition, polycarbonate obtained using halogen-containing bisphenol and halogen-containing phenol as starting materials is known (Japanese Patent Application Laid-Open No. 136796/1976). This polycarbonate, however, is not sufficiently high in impact resistance and fluidity although it is produced using three or more different halogen-containing bisphenols as starting materials.